1. Field
The present disclosure relates to a light emitting diode (LED), and more particularly, to an LED with a high brightness output.
2. Background
Light emitting diodes (LED) have been developed for many years and have been widely used in various technology areas. Because LEDs have better electrical power to light conversion efficiency than the conventional incandescent lighting and longer lifetimes than both the conventional incandescent and fluorescent light sources, they have been good candidates for replacing these conventional light sources.
The brightness or luminance of an LED is an important quality that specifies how it will illuminate a particular location. For applications such as rear projection TVs, presentation projectors, and automobile headlights, among others, the brightness is a particularly important factor.
The light brightness or luminance (L) of a light source is proportional to the optical power (φ) of the light source, as shown below:L=φ/(AΩ),where A is an area of the source and Ω is a solid angle of light emission.
Typically, the area (A) and the solid angle Ω are constant. Therefore, traditionally, the current supplied to the LED must be increased to increase the luminance. Increasing the current, i.e., increasing the current density, however, also decreases the reliability of the LED. Even if the reliability of the LED is not a concern, once the current density is above a certain limit, the optical power will “roll over,” resulting in a decrease in brightness. Increasing the current density also increases the power density or the heat generated per unit area, which is not a desirable result.
Accordingly, there is a need in the art to achieve an increase in the brightness of the LEDs without increasing current or power density.